Hydraulic braking apparatus



March 24, 1953 J. H. BRoDlE 2,632,301

HYDRAULIC BRAKING APPARATUS Filed Aug. 5l, 1950 JAMES AC 5200/5, INVENTOR.

.4 7TOP/VEYS Patented Mar. 24, 1953 UNITED STATES PATENT OFFICE 2,632,301 HYDRAULIC .BRAKING PPARATS 'James H. Brodie, Baltimore, Md. Application August 31, 1950, Serial No. 182,538

This invention relatesM to the regulation of flow of a hydraulic fluid by means of an orice of variable area which can be adjusted orset to a size aiording a desired amount of restriction of and resistance to the fluid iiow and thus building upa desired amount of back pressurev in the line leading to the oriice. More particularly, the invention relates to apparatus of the above type that is responsive to variations occurring in such back pressure so as to area ofthe orice, without changing the setting of the apparatus, in order to maintain a substantially uniform back pressure corresponding to said setting regardless of variations or" pressure in the source to which the line is connected.

Apparatus of the type characterized above can be used in any hydraulic system in which it is desired to maintain a substantially constant resistance to flow of a pressure uid, or in other Words a substantially constant back pressure in a hydraulic pressure line. Such apparatus is especially useful in connection with hydraulic braking systems, generally speaking,'wherein the orifice ,restriction is opposed to a pumping eiTort for any desired purpose. For instance, the invention can be utilized in the foregoing manner to retard or brake the movement of various types of moving bodies, such as rotary cylinders, rolls or drums, moving vehicles, and the like, It is particularly suited for application to hydraulically` driven machines or mechanismsin which the ,driving motor may alsoserve asa pump op; erating against a controllable back pressure. The accompanying drawing illustrates dialgrammatically the'application'of the invention to the braking of ahydraulic driving motor, but itis to be expressly understood that'this embodiment is by Way of example only and thatthe'drawing is not to be construed as a definition of the'limits of the invention, reference being had to the appended claims for this purpose.

Referring to the drawing, I indicates a hydraulic driving motor of any suitable'type for driving or operating any desired moving body.` A supply of hydraulic pressure liquid is maintained in 'alreservoir 2 from which the liquid isV drawn through apipe 3 to the suction side of a pump il of any suitable type which delivers the liquid under pressure through a pipe 5 and asuitable valve -6 Ato 'the motor I. The liquid discharged trom the motor'returns to the reservoir by way of a pipe l, a suitable valve 8, and a pipe `9. Itl will be understood that the apparatus thus far described is typical of various known types of hvsilauliedrripe-erperat adjust automatically the 5 claims. (01..,607-53) 2- Whenvit is desired to retarder brake the rota? tion of the driving motor I, the valve 6 isshiited to the position shown inthe drawing, cuttingvpfi the supply of pressure liquid to the driving motor. In Vcase the `main pump li continuestooperate under these conditions and inr order to, prevent building up an excessive pressure in the line'v'A, a pressure relief valve I0 Vof any suitabletype may be provided in a pipe II connectingtlfie pipes v5 and 9. The motor I, being' drivingly connected to the moving body,`now continues to operate as a pump. v The valve 8 being also shifted to the position shown in the drawing, the liquid pumped by the motor I flowsV through the valve 8 and through a pipe I2 to a'suitable'fiowlconstricting device indicated generally at I3, from .whichy the liquid returns by way of a pipe lli, thej valve Sfand the pipe 5 to the intake side of the motor.; vThe valves 6 and 8 may be of any suitableVv type and as shown comprise three-way valves movable t@ two positions apart. Preferably thesev valves are'connected in any'suitable manner for simultaneousr operation between these two positions; and as indicated diagrammatically inthe 'dravvf ings, the valve operating-armsI l'and` 'ljfare linked together by a rod AII which can be shifted by means of a suitable handle I8; Y The magnitude of the braking effectA is deter; mined by the yrestriction o f flow, provided by the device I3 which comprises a variable orifice 'of any suitable type. -In the form shown,thisfdejv vice comprises a tapered substantially conical inlet opening I9 in which is movable, the tapered end 20 of a rod `2I sliding in alpacking 22. The rod ZI is moved by a hydraulic operating de'v'ic of any suitable` type, herevshown as comprising a two-part casing 23,l 24 bolted together at' 25 and attached at 26 to the now-restricting device I3. The lower end of the rod 2l carries' a piston head 21 which is urged in a direction to withdraw the tapered end 20 from ythe opening I9 by suit'- able resilient means such as a coil spring 428;Y The rod 2|' is moved inthe oppositeY direction', compressing the spring 2'8, when hydraulic'presl sure uid is admitted to the lowerend of the casing 23, '24 through a pipe 29, thus advancing the rod 20, l2I into the opening'l9 .and'prog'res sively restricting the orifice areal f '7 ff Adjustable means are provided for moving vthe rodZI initially to a position corresponding to a desired back pressure that is to be maintained in the pipe 1. As the motor `I slows down, howl`` ever, its pumping effort decreases and accord.- ingly the .back pressure in the pipe 1 decreases and the .retarding or braking (effect 'isdiniinished 3 In order to maintain the back pressure substantially constant at the desired value for which the apparatus is initially set, therefore, the adjustable means mentioned above is responsive to said back pressure in such a way as to compensate for variations of Said back pressure. Preferably these objectives are accomplished by the provision of a suitable valve for controlling the supply of hydraulic operating uid to the piston 21, said valve being movable in one direction by resilient means that are settable to determine the Value of the back pressure to be maintained in the pipe 1, and being moved in the opposite direction by hydraulic means responsive to said back pressure in the pipe 1.

In the form shown, the pipe 29 which supplies hydraulic operating fluid to the piston 21 is connected to the outlet port 39 of a valve body 3l having a threaded cap 32. The inlet port 33 of the valve body is connected by a pipe 34 to a suitable pump 35 which'draws uid from the reservoir 2 by means of a pipe 36 and supplies said fluid under suitable pressure through the valve 3l and pipe 29 to the piston 21. When the valve 3| is closed, and in order to prevent building up an excessive pressure in the pipe 34, a by-pass pipe 31 and pressure relief valve 38 may connect the pipe 34 to the reservoir 2,

The valve body 3l contains a piston valve 39 provided with a circumferential groove 49 which, in the open position of the valve shown in the drawing, is aligned with the valve ports 36 and 33. The piston 39 is normally maintained in this position by a spring 4I acting against the piston head 42 which engages a shoulder 43 in the valve body 3 I. However, the valve piston can be moved to closed position against the spring 4I by hydraulic pressure in the chamber 44 at the opposite end of the piston 39, said chamber being connected by a pipe 45 with the pipe I2 at a point between the motor I and the flow-restricting device I3.

The Supply of pressure uid to the piston 21 results in progressive restriction of the orifice I9, 29 and in progressive increase in the back pres- VSureV in the pipe 1 whichrback pressure is transmitted through the pipe 45 to the chamber 44. When this pressure exceeds the compression of the spring 4I, the valve piston 39 is moved to closed position to cut off the supply of pressure fluid to the piston 21, after which the tapered rod 29, 2| remains stationary until there is a further variation in the back pressure in the pipe 1. The position which the rod 20, 2I assumes initially, therefore, depends on the loading of the spring 4I which can be varied in any suitable manner. The drawing illustrates a system adapted for manual control of the spring loading, and to this end the upper end of the spring is engaged by the head 46 of a rod 41 which passes out of the cap piece 32 through a suitable gland 48 into engagement with a loading ydevice 49 operated by a link 59 and a handle I.

When it is desired to discontinue the braking effect, the pressure in the pipe 29 is relieved by connecting this pipe through a suitable relief valve back to the reservoir 2. In the form shown, a branch 52 of the pipe 29 is connected to a relief valve body 53 which is in turn connected by a pipe 54 with the reservoir 2. Escape of the pressure liquid from the pipe 29 is controlled bya valve 55 urged toward closed position by a spring 56. In'order to prevent opening of the valve 55l when the braking effect is in use, the

spring 56 may be loaded simultaneously with the spring 4I by any suitable means here shown as comprising a head 51 on the end of a rod 58 which passes out of the valve body 53 through a gland 59 and into engagement with the loading device 49 mentioned above. The valve rod 69 which carries the valve 55 may be extended into a recess in the rod 58 for guiding purposes. When the handle 5I is operated to load the valve 39, the valve 55 is simultaneously loaded suiciently to prevent'its opening by the pressure developed by the pump 35. When the handle 5I is 'moved in the opposite direction, however, the spring 56 is unloaded and in this condition is weaker than the spring 26 so that the valve 55 opens, Now the liquid discharged by the pump 35 passes through the valves 39 and 55 and returns to the reservoir through the pipe 54, and also the piston 21 gradually descends and withdraws the tapered rod 29, 2I fro-m the opening I9 of the flow-restricting device I3.

The operation of the system may be summarized briefly as follows. When the motor I is being driven by the pump 4, the valves 6 and 8 are shifted in a clockwise direction through an angle of so that no liquid iiows from the moto-r I to the flow-restricting device I3. The handle 5I being released, there is no loading of the springs 4I and 56. The valve piston 39 occupies the position shown in the drawings, but the valve 55 is open, the piston 21 occupies its lowermost position, and the liquid circulated by the pump 35 passes through the vvalves 39 and 55 and returns to the reservoir 2. When it is desired to retard the motor I, the valves 6 and 8 are shifted back in a counterclockwise direction to the position shown in the ldrawing so that the motor operates as a pump circulating liquid through the orifice I9, 29. The handle 5I is now depressed to any desired degree, loading the springs 4I and 56 and closing the valve 55. The pressure liquid circulated by the pump 35 now enters the casing 24 and lifts the piston 21 and rod 2| to decrease the orifice area and to increase the back pressure in the pipe 1. When this Iback pressure reaches a value such as to overcome the loading of the spring 4Iy the piston valve 39 is shifted to closed position and the rod 2I becomes stationary.

The apparatus is thus set initially to provide a desired degree of retarding or braking effect on the motor I. However, this retarding action gradually slows down the motor and decreases the amount of liquid circulated by it through the orice I9, 29 with the result that the braking effect is diminished. This result is reflected in a decrease of back pressure in the pipe 1 so that the spring 4I comes into action to move the piston valve 39 again to the open position shown in the drawings. The pump 35 is again able to `deliver pressure liquid to 'the piston 21 an-d to move the tapered rod 2|), 2I further into the opening I9, thus decreasing the orifice area and increasing the back pressure in the pipe 1 until it again overcomes the spring 4I and moves the piston valve 39 to closed position. This action continues automatically as long as the position of the loading device 49 is maintained, and thus maintains the back pressure in the pipe 1 at a substantially constant value corresponding to the initial setting of the apparatus. This setting can be varied at any time by shifting the position of the handle 5I.

When braking effect is no longer desired and the handle 5I is released land restoredto "its neutral or inoperative position, the spring 56 is unloaded and the valve 55 opens as explained above, thus permitting the piston 21 to descend and the rod 20, 2| to be withdrawn until the orifice is opened to the full extent ready for the next braking operation.

While only one embodiment of the invention has been described and illustrated in the drawing, it will be understood that the invention is not'l restricted to this embodiment and that various changes may be made in the form, details of construction, and arrangement of parts without departing from its spirit. Reference, therefore, should be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a hydraulic system having a hydraulic pressure line connected to a source of varying pressure, means for constricting the ow of hydraulic uid in said line and maintaining a substantially constant back pressure therein comprising a movable member for variably restricting the ilow through said line, hydraulically operated means for moving said member, a source of hydraulic pressure connected to said hydraulically operated means, a relief valve connected to the pressure line between said source of hydraulic pressure and said hydraulically operated means for relieving pressure therein and returning said member to normal position and means for controlling the supply of fluid to said hydraulically operated means and thereby regulating said back pressure comprising a valve, resilient means for moving said valve to open position, and means subjected to said back pressure for moving said valve to closed position against said resilient means.

2. In a hydraulic system pressure line connected to having a hydraulic a source of varying pressure, means for constricting the flow of hya draulic fluid in said line and maintaining a substantially constant back pressure therein comprising a member movable in one direction to progressively restrict the ow through said line, hydraulically operated means for moving said member in said one direction, moving said member in ated means, means for simultaneously loading said control valve toward open position and said relief valve toward closed position, and means subjected to said back pressure for moving said control valve to closed position when said back pressure exceeds a value corresponding to the loading of said control valve.

3. A hydraulic driving system for a vehicle comprising a hydraulic driving rotor for a wheel of the vehicle which is drivable by said Wheel as a hydraulic pump, hydraulic braking means including a flow-restricting device having a movable member for variably restricting liquid flow therethrough, valve means for connecting said rotor to said device to pump liquid therethrough, hydraulically operated means for moving said member to a flow-restricting position corresponding to a desired braking elect, a source lof hy- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 569,781 Brown Oct. 20, 1896 1,156,165 McManamy Oct. 12, 1915 1,190,799 Ren July 11, 1916 1,664,493 Smith Apr. 3, 1928 1,690,093 Allen Nov. 6, 1928 2,275,321 Scates Mar. 3, 1942 2,413,162 Ackerman Dec. 24, 1946 2,445,573 Godbe July 20, 1948 

